Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes /issues, but are citable by Digital Object Identifier (DOI).
Display Method:
State Feedback Generalized H2 Control for Continuous Integrated Control System
SUN Fengqi
 doi: 10.21656/1000-0887.420169
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Abstract:
Based on Lyapunov stability theory, matrix analysis method, linear matrix inequality methods, etc, the generalized H2 control of singularly perturbed uncertain control systems with time-varying delay and control input and disturbance input is studied. A memory state H2 generalized controller is designed, the decision theorem of the specific design method given. Quoting new lemma for delay dependent and delay independent cases, the relatively less conservative stability criterion is derived. The obtained results are linearized, the selected numerical examples are used to verify the effectiveness and feasibility to the derived conclusions. It is pointed out that the closed-loop system is asymptotically stable in the whole range from zero to singular perturbation upper bound, which expands the generalized H2 stability space and reduces the L2-L performance index. By comparing the stability state parameter index with the related literatures, it is shown that the proposed method has certain advantages and less conservatism, and is suitable for standard and non-standard cases.
Size-Dependent Effect of Micro-Nano Mindlin Plate Based on Couple Stress Theory
XUE Jianghong, HE Zanhang, XIA Fei, LI Zerong, JIN Fusong, YANG Peng
 doi: 10.21656/1000-0887.420171
Abstract(31) HTML(19) PDF(2)
Abstract:
A Mindlin plate theory for micro-nano structures is proposed based on couple stress theory. A length scale parameter was introduced to take into account the scale effect and the constitutive equations of the micro-nano Mindlin plate were derived by considering the transverse shear deformation. The governing equations in terms of displacements and the slope functions of buckling and free vibration for shear deformation micro-nano plate were further deduced from force equilibrium conditions. The analytical solutions of buckling and free vibration for shear deformation micro-nano plate were obtained by separating the displacement and rotation variables in space and time domains. Two scenarios of boundary conditions were analyzed: SSSS (simply supported by four edges) and SCSC (two opposite edges simply supported and other two edges clamped). A MATLAB program was developed to compute the critical buckling and natural frequency with different value of scale ratio, aspect ratio and length-to-thickness ratio. The theoretical solutions are compared with the results from ABAQUS finite element analysis and the predictions obtained from existing studies and found in good agreement with the other two methods. The results show that the scale effect has a significant effect on the buckling load and the natural frequency.
Stochastic Model Updating Based on Kriging Model and Lifting Wavelet Transform
WU Yucheng, YIN Hong, PENG Zhenrui
 doi: 10.21656/1000-0887.420128
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Abstract:
In order to improve the efficiency of stochastic model updating and reduce the amount of calculation, a stochastic model updating method based on Kriging model and lifting wavelet transform is proposed. Firstly, perform lifting wavelet transform on the acceleration frequency response function, and extract the fifth-level approximate coefficients to replace the original frequency response function; secondly, use the Latin hypercube sampling to sample the parameters to be updated and the corresponding approximate coefficients as the outputs to build the Kriging model. A butterfly optimization algorithm with the Lévy flight (LBOA) is proposed and use to improve the accuracy of the Kriging model; finally, with the goal of minimizing the Wasserstein distance, the mean value of the parameters to be updated is solved by the whale optimization algorithm. The results of the test function show that LBOA has greatly improved in terms of optimization, convergence accuracy and stability. The updating errors of the numerical examples are all less than 0.4%, verifying that the proposed model updating method has high accuracy and efficiency.
Explicit Solutions for Wave Equation of Nonlinear Elastic Rod
GUO Peng, TANG Rongan, SUN Xiaowei, HONG Xueren, SHI Yuren
 doi: 10.21656/1000-0887.420245
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Abstract:
The sine-cosine method is applied to the wave equation of nonlinear elastic rod, and some new periodic and soliton solutions of the equation is obtained (material constant n is a constant different from 1). The graphs of some solutions are given through math software. The results are helpful to further research on existence of solitary waves in the nonlinear elastic rod.
Mesoscopic Numerical Study on Flow Boiling Heat Transfer Performance in Channels With Multiple Rectangular Heaters
LI Yingxue, WANG Haoyuan, LOU Qin
 doi: 10.21656/1000-0887.420325
Abstract(16) HTML(23) PDF(1)
Abstract:
The flow boiling phenomenon in a channel with multiple rectangular heaters under constant wall temperature was numerically studied by lattice Boltzmann method. The effects of distance between/among heater, heater length and heater surface wettability on bubble morphology, bubble area and heat flux of the heater surface were studied. The results show that the bubble growth rate increases with the increase of the distance between/among heaters, the larger bubble area promotes the nucleated bubbles to leave the heater surface in advance, and the corresponding boiling heat transfer performance increases by 12% with the increase of the distance between/among heaters from 250 lattices to 1000 lattices. On the other hand, the longer the heater length, the earlier the bubble nucleation time and separation time from the heater surface, and the better the boiling heat transfer performance, and the boiling heat transfer performance increases by 13% with the increase of the heater length from 16 lattices to 22 lattices. In addition, the bubble nucleation time of the hydrophilic surface is later than that of the hydrophobic surface. Compared with the hydrophilic surface, there are residual bubbles on the hydrophobic surface after the bubbles leave the heater. The average heat flux and bubble area of hydrophilic surface are less than those of hydrophobic surface. When the contact Angle changes from 77° to 120°, the heat transfer performance increases by 26%. Finally, through the orthogonal test scheme, it is found that the wettability of the heat exchanger surface has the greatest influence on the flow boiling heat transfer performance, while the heater length has the least influence on the flow boiling heat transfer performance.
Sampling Consensus of Second-Order Multi-Agent Systems Based on Time-Varying Topology
ZHENG Liying, YANG Yongqing, XU Xianyun
 doi: 10.21656/1000-0887.420220
Abstract(17) HTML(19) PDF(3)
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The sampling consensus of second-order multi-agent systems with time-varying topology is investigated based on the constant position difference and consistent speed. Firstly, the virtual leader is introduced and the sampling consensus problem of multi-agent systems is transformed into the stability problem of the corresponding error system. Secondly, by estimating the sampling error, the influence of sampling error on system consistency is studied. Finally, by virtue of the Lyapunov stability theory, the stability of the constructed error system is analyzed, and a sufficient condition for the stability of the error system is given. The numerical simulation results verify the effectiveness and correctness of the theoretical analysis.
Research on the Deposition and Orientation Characteristics of Cylindrical Particles in a Gas-solid Two-phase Turbulent Flow Through a Curved Tube
LI Liang, SHI Ruifang, LIN Jianzhong
 doi: 10.21656/1000-0887.420320
Abstract(40) HTML(30) PDF(5)
Abstract:
In the case of Reynolds number Re=3000 ~ 50000, Stokes number St=0.1 ~ 10, Dean number De=1400 ~ 2800, the orientation and deposition characteristics of cylindrical particles with aspect ratio β=2 ~ 12 in a turbulent flow through a curved tube are studied. The motion of cylindrical particles is described by the slender body theory combined with the Newton's second law. The orientation distribution function of cylindrical particles is given by the Fokker Planck equation. The mean velocity of the flow is obtained by solving the Reynolds-averaged Navier-Stokes equation and Reynolds stress equation. The turbulent fluctuating velocity acting on particles is described by the kinetic simulation sweeping model. By solving the equations of turbulent flow and particle motion and orientation distribution function, the orientation distribution of particles on the cross-section at different axial positions and outlet is obtained and analyzed. The effects of various parameters on the deposition rate of particles are discussed. The results showed that the main axis of particles tends to the flow direction with the increase of St and β, and the decrease of De and Re. Deposition rate of particles increases with increasing De, Re and β. However, it shows a non monotonic trend with the change of St. Conclusion has reference value for practical engineering application.
Analysis and Simulation of Natural Frequencies of a Slightly Curved Pipe
Jiarui YUAN, Hu DING, Liqun CHEN
 doi: 10.21656/1000-0887.420299
Abstract(39) HTML(23) PDF(16)
Abstract:
For the transverse vibration of slightly curved pipe, a dynamic mechanical model based on Timoshenko beam theory is established for the first time. The natural vibration characteristic of slightly curved pipe under the influence of the fluid flow is analyzed. With generalized Hamiltonian principle, the governing equation of the transverse vibration of slightly curved pipe considering the effect of fluid-structure coupling is derived. Based on Galerkin truncation, the natural frequencies of slightly curved pipe are obtained by generalized eigenvalue method. Effects of the fluid velocity and the initial deflection on the natural vibration characteristic of the pipe are studied. The equivalent stiffness and equivalent damping method base on finite element simulation for the natural vibration of the slightly curved pipe are developed. Then through the finite element numerical simulation software, the results of Galerkin truncation method and the effectiveness of the Timoshenko model are verified. The results show that fluid velocity and the initial bending degree both have significant effects on the natural frequencies of slightly curved pipe.
An Improved Third Order WENO Scheme Based on a New Reference Smoothness Indicator
Yahui WANG
 doi: 10.21656/1000-0887.420194
Abstract(59) HTML(16) PDF(6)
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In order to meet the requirement of high accuracy and high resolution in computational fluid dynamics (CFD), a new reference smoothness indicator is proposed to reduce the numerical dissipation of the classical third-order weighted essentially non-oscillatory (WENO) scheme.Its construction method is different from the classical WENO-Z scheme. It is obtained by the $ L^2$-norm approximation of the linear combination of the derivatives of the reconstruction polynomials of the candidate sub-stencils and the derivatives of the reconstruction polynomials of the whole global stencil.Using this calculation method, higher-order reference smoothness indicators can be obtained than WENO-Z scheme. In addition, different reference smoothness indicators can be obtained by changing the value of free parameter $ \varphi$. The effectiveness of the reference smoothness indicator is proved by a series of numerical examples.
Generalized Degrees of Freedom for Loading on the Crack
Hua XU, Zheng CAO, Yunpeng ZOU, Lüfeng YANG
 doi: 10.21656/1000-0887.420317
Abstract(32) HTML(31) PDF(4)
Abstract:
Service with cracks is the normal state of engineering structures, because the fluid invades into the crack, the crack surface is loaded directly, which makes the crack further expand, and even affect the safety of the structure. In the analysis of fracture problems, the Williams element with generalized degrees of freedom (W element) uses the Williams series to establish the displacement field of the singular zone of the crack tip, and the stress intensity factor, (SIFs) can be directly obtained by solving the generalized stiffness equation, which has high precision and high efficiency, but the W element needs to satisfy the free boundary condition of the crack surface in the singular zone, so it is limited in the analysis of crack surface loading. Based on the SIFs reciprocity, the load on the crack surface is equivalent to the concentrated force on the crack surface at the periphery of the singular zone in the equivalent singular zone, so the load on the crack surface in the singular zone can be avoided, so the W element can be used for simple calculation. The analysis of numerical examples show that the size of the equivalent singular zone is 1/20 length of the crack, and the equivalent load coefficient P suggests that the calculation accuracy of 2.0, and the calculation accuracy of W element meets the error limit of 1%. It is proved that the equivalent treatment method of crack surface loading in singular zone is reasonable and universal, and overcomes the limitation of W element in analyzing the loading problem of crack surface.
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2022, Volume 43, Issue 6 publish date:June 01 2022
Display Method:
Dynamics and Control
Beat Vibration of X-Configuration Tension Nonlinear Systems Under Resonance Excitation
QI Zihan, WU Zhiqiang, JIAO Yunlei, JIA Wenwen
2022, 43(6): 597-607.   doi: 10.21656/1000-0887.420326
Abstract(36) HTML(22) PDF(26)
Abstract:

The circular membrane solar array has attracted extensive attention due to its high storage ratio and strong power supply capability. In order to adjust the tension of large film structures, a tension adjusting device composed of ropes and springs is usually introduced, and its mechanical characteristics are highly nonlinear, with the effects rarely studied yet. Aimed at the tension adjustment, a mechanism model was proposed. The nonlinear dynamics equation for the 2DOF system was established with the Lagrangian energy method. With an engineering prototype as the example, the responses of the tension mechanism with unsymmetrical ribs under resonance excitation were studied. The results show that, the change of the excitation amplitude has an important influence on the characteristics of the beat response of the system. Consequently, the responses of the system exhibit chaotic, almost periodic and multifold periodic phenomena. The research makes an important reference to the parameter design of tension mechanisms.

The RBF-PU Method for Solving 2D Nonlocal Diffusion and Peridynamic Equations
ZHANG Shangyuan, NIE Yufeng, LI Yiqiang
2022, 43(6): 608-618.   doi: 10.21656/1000-0887.420295
Abstract(121) HTML(46) PDF(35)
Abstract:

The radial basis function partition of unity (RBF-PU) method  was applied to obtain the numerical solution of 2D nonlocal diffusion and peridynamic problems. The main idea is to partition the original domain into several patches, use the RBF approximation on each local domain, and then give weighting to obtain the global approximation of the unknown function. The radial basis function method based on the strong form of the equation has many advantages, such as avoiding an additional layer of integral calculation, no need to deal with intersections of neighborhoods with the mesh, and easiness of implementation. The numerical results show that, this method can solve nonlocal diffusion equations and peridynamic equations accurately and efficiently.

Non-Smooth Grazing Dynamics for Cantilever Beams With Bilateral Elastic Constraints
SHI Meijiao, XU Huidong, ZHANG Jianwen
2022, 43(6): 619-630.   doi: 10.21656/1000-0887.420177
Abstract(59) HTML(31) PDF(15)
Abstract:

The grazing-induced non-smooth dynamical behaviors of single-degree-of-freedom cantilever beam systems with bilateral elastic constraints were studied. Firstly, based on the dynamical equations for the cantilever beam under elastic impacts and the definition of grazing points, the existence condition for the bilateral grazing periodic motion was analyzed. Secondly, the zero-velocity Poincaré section was selected to derive the high-order discontinuous mapping with parameters near bilateral grazing orbits. Then a new composite piecewise normal form mapping was established through combination of the smooth flow mapping and the high-order discontinuous mapping. Finally, the validity of the high-order mapping was verified through comparison of the bifurcation diagram of the low-order mapping with that of the high-order mapping, and the grazing dynamics of the cantilever beam under elastic impacts were further revealed through numerical simulation.

Solid Mechanics
A Study on Interfacial Fracture Behaviors of Superconducting Thin Film/Substrate Structures on Taking the Account of Effects of Flux Flow
DING Jieying, XUE Feng, GOU Xiaofan
2022, 43(6): 631-638.   doi: 10.21656/1000-0887.420353
Abstract(77) HTML(59) PDF(24)
Abstract:

The superconducting thin film is a kind of multilayer structure prepared by chemical coating. As a conductive functional structure material with excellent performance, its structural integrity is directly related to the current-carrying capacity. During the preparation of superconducting thin films, it is hard to avoid the interface cracks between the superconducting layer and the metal substrate. In this case, along with the current-carrying operation, the strength of the interface crack in an external magnetic field makes a key problem. Therefore, based on the theory of flux through the thin film and the linear elastic fracture, an analytical model was established for the strength of the interface crack between the superconducting film and the substrate. The effects of the viscous flux flow on the stress field and the energy release rate at the crack tip were obtained. The results show that, the higher the flux flow velocity is, the greater the stress and the energy release rate at the crack tip of the interface will be, which will lead to crack propagation along the interface. The work is helpful for the analysis of interface cracks mentioned above.

The Anti-Plane Problem of Collinear Interface Cracks Emanating From a Circular Hole in 1D Hexagonal Quasicrystal Bi-Materials
ZHANG Bingcai, DING Shenghu, ZHANG Laiping
2022, 43(6): 639-647.   doi: 10.21656/1000-0887.420202
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Abstract:

The anti-plane problem of asymmetric collinear interface cracks emanating from a circular hole in 1D hexagonal quasicrystal bi-materials was studied. With the Stroh formula and the complex function method, the complex potential functions under the coupling action of the phonon field and the phason field were obtained. The analytical expressions of the stress intensity factor (SIF) and the energy release rate (ERR) at the crack tip were given. The effects of the circular hole radius and the crack length on the SIF, and the effects of the coupling coefficient, the phonon field stress and the phason field stress on the ERR, were discussed. The results show that, the SIF tends to be stable with the increase of the right crack length for a constant circular hole radius. For a certain phason field stress value, the ERR reaches the minimum value, which indicates that a specific phason field stress can inhibit the crack growth.

Research on Topology Optimization of Damping Material Microstructures With Varied Volume Constraints
ZHANG Dongdong, LUAN Fuqiang, ZHAO Lihui, ZHENG Ling
2022, 43(6): 648-659.   doi: 10.21656/1000-0887.420206
Abstract(45) HTML(21) PDF(21)
Abstract:

The vibration suppression performance of a damping composite structure depends on the material layout and the damping material properties. A topology optimization method was proposed for damping material microstructures with varied volume constraints, to obtain the damping material microstructure with desired properties under the smallest material consumption. Based on the homogenization method, a 3D finite element model for the damping material was established, and the effective elastic matrix of the damping material was formulated. The Hashin-Shtrikman bounds theory was used inversely to estimate the volume fraction bound of the damping material corresponding to the desired effective modulus, and a movement criterion for volume constraint bounds of damping materials was constructed. Then the optimization problem of achieving the desired properties of damping materials with microstructures was converted to another problem of maximizing the desired modulus under volume constraints, and a topology optimization model for the damping material microstructure was established. The optimality criteria method was employed to update the design variables, and the optimized topology configurations of damping material microstructures were obtained. The feasibility and effectiveness of the proposed method were verified with several numerical examples, and the influences of the initial configurations, the mesh density and Young’s modulus on the microstructure configurations of the damping material were also discussed.

PDDO Analysis of 2D Transient Heat Conduction Problems
ZHOU Baoliang, LI Zhiyuan, HUANG Dan
2022, 43(6): 660-668.   doi: 10.21656/1000-0887.420150
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Abstract:

The peridynamic differential operator (PDDO) theory was introduced to solve the 2D transient heat conduction problems. The heat conduction equation and the boundary condition were reformulated from the local differential form to the non-local integral form. Then the Lagrangian multiplier method and the variational analysis were used, and a non-local model for 2D transient heat conduction problems was established. Through error and convergence analysis, the accuracy of this model was verified in comparison with the results of other numerical methods. The model was further applied to solve the 2D transient heat conduction problems of plates with irregular boundaries and micro-defects (cracks and holes). The results show high accuracy, wide applicability and good convergence of this method, which provides new insights into the 2D transient heat conduction problems.

Applied Mathematics
Effects of Intraspecific Competition Delay on Vegetation Periodic Oscillation Patterns
LI Jing, SUN Guiquan, JIN Zhen
2022, 43(6): 669-681.   doi: 10.21656/1000-0887.420190
Abstract(69) HTML(65) PDF(14)
Abstract:

Aimed at the phenomenon of competing for water resources between young vegetation and adult vegetation in arid and semi-arid areas, a vegetation-soil water dynamic model with intraspecfic competition delay was established. The conditions for the existence of an unique vegetation survival equilibrium and the local stability of the vegetation extinction equilibrium were analyzed. The generating conditions for Hopf bifurcating periodic solutions of non-spatial and spatial systems were given, respectively. The periodic oscillation pattern appearing in the vegetation evolution with time was numerically simulated. Through the parameter sensitivity analysis, the rainfall and the vegetation growth rate were found to have significant influences on the generation, the amplitude and the period of this pattern, while the effects of evaporation was found to be the least significant. The results indicate that, the rainfall and the vegetation properties have profound impacts on the evolution and development of vegetation in arid and semi-arid areas. The introduction of spatial diffusion inhibits the occurrence of this pattern, but doesn’t affect the amplitude and the period. The work explains the phenomenon of vegetation periodic oscillation widely observed in nature, and provides theoretical supports for the sustainable development of the vegetation system.

Characterizations of Approximate Optimality Conditions for Fractional Semi-Infinite Optimization Problems With Uncertainty
FENG Xinyi, SUN Xiangkai
2022, 43(6): 682-689.   doi: 10.21656/1000-0887.420248
Abstract(74) HTML(39) PDF(35)
Abstract:

A class of multi-objective fractional semi-infinite optimization problems with uncertain data were investigated. Firstly, a robust optimization model corresponding to the uncertain multi-objective optimization problem was introduced. Then the optimization model was converted to a multi-objective optimization problem with the Dinkelbach method. In turn, by means of the scalarization method, the corresponding scalarization optimization problem was built, and the relationship between robust solutions to the multi-objective optimization problem and its corresponding scalarization optimization problem was described. Finally, through a robust-type sub-differential constraint qualification, the robust optimality condition for approximate quasi-efficient solutions to the multi-objective fractional optimization problem was established.

Dynamic Analysis of the Network Epidemic Model Based on White Noise
CAO Xiaochun, JING Wenjun, JIN Zhen
2022, 43(6): 690-699.   doi: 10.21656/1000-0887.430009
Abstract(77) HTML(41) PDF(21)
Abstract:

Based on the deterministic network infectious disease model, a stochastic network infectious disease model under the influence of white noise was established, and the existence and uniqueness of the global solution to the model were proved. With the theory of stochastic differential equations, sufficient conditions for stochastic extinction and persistence of infectious diseases were obtained. The results show that, white noise has a great impact on the transmission dynamics of network infectious diseases. White noise can effectively suppress the spread of infectious diseases, and large white noise can even make the original persistent infectious diseases become extinct. Finally, the theoretical results were verified through numerical simulations.

Analysis of the Finite Point Method for Fractional Cable Equations
CHEN Hongling, LI Xiaolin
2022, 43(6): 700-706.   doi: 10.21656/1000-0887.420183
Abstract(40) HTML(8) PDF(21)
Abstract:

With the central difference scheme to discretize the Riemann-Liouville time fractional derivatives and by means of the finite point method to establish discrete algebraic equation systems, a meshless finite point method was proposed for the numerical analysis of the fractional Cable equation. The error estimation of the method was derived and discussed in detail. Numerical examples verify the efficiency and convergence of the method and confirm the theoretical results.

Damage Identification for Bridge Structures Based on the Wavelet Neural Network Method
XIAO Shu-min, YAN Yun-ju, JIANG Bo-lan
2016, 37(2): 149-159.   doi: 10.3879/j.issn.1000-0887.2016.02.004
[Abstract](1142) [PDF 5386KB](734)
摘要:
桥梁结构在服役期间会承受复杂的荷载,长期使用会不可避免地出现各种损伤。若这些损伤不能被及时发现和适当处理,将有可能造成严重的事故。因此,桥梁结构的局部小损伤识别对于其及时检修有重要意义。通常,损伤结构的全局动态特性测试可能对局部的结构损伤不敏感,特别是对小损伤,这就需要从结构动态响应信号中提取对损伤更敏感的特征量。建立了桥梁结构的有限元模型并进行动力特性分析;采用小波包分析方法处理结构动态响应信号以构造结构损伤指标,并结合结构损伤指标和人工神经网络方法进行桥梁结构的损伤定位.
The PseudoExcitation Method and Its Industrial Applications in China and Abroad
LIN Jia-hao, ZHANG Ya-hui, ZHAO Yan
2017, 38(1): 1-31.   doi: 10.21656/1000-0887.370578
[Abstract](1192) [PDF 1039KB](1418)
摘要:
《随机振动的虚拟激励法》自1985年正式发表以来,逐渐得到许多工程领域的认可和采用,解决了很多重要而困难的工程问题.该方法不但被国内某些工程规范所推荐,而且被3种国际工程手册成章刊载,在国际上亦占有了一席之地.该文是笔者参考了数百篇国内外论文,依据其中一部分在11个工程领域对虚拟激励法的应用和一些学者的评论所撰写的综述.借以让更多工程技术人员和研究者对虚拟激励法有较为全面的了解,以结合各自工程领域更有效地开展对随机振动理论和方法研究成果的应用和发展.
Uncertainty Quantification for System Identification Utilizing the Bayesian Theory and Its Recent Advances
YAN Wang-ji, CAO Shi-ze, REN Wei-xin.
2017, 38(1): 44-59.   doi: 10.21656/1000-0887.370571
[Abstract](1094) [PDF 647KB](944)
摘要:
受测试误差、建模误差、数值离散化以及环境变异等因素的影响,结构系统识别过程不可避免地存在不确定性,因此有必要引入概率统计方法来提高其鲁棒性,为工程结构安全监测提供更为可靠的结果.近年来,Bayes(贝叶斯)方法因为其诸多优势在系统识别领域受到了广泛关注.该文梳理了Bayes系统识别的历史脉络和研究进展.从Bayes系统识别的理论框架出发,分析了量化系统识别不确定性两类方法的适用条件与局限性.此外,文章综述了Bayes方法在模态参数识别、有限元模型修正以及结构损伤识别方面进行不确定性分析的理论、实现及其应用.最后对基于Bayes方法进行系统识别研究的发展趋势做出了展望.
Convergence Results on Heat Source for 2D Viscous Primitive Equations of Ocean Dynamics
LI Yuanfei
2020, 41(3): 339-352.   doi: 10.21656/1000-0887.400176
[Abstract](699) [FullText HTML](76) [PDF 405KB](288)
摘要:
考虑了在一个柱形区域上的海洋动力学中二维黏性方程组解的收敛性.在此模型中存在一个关键的参数就是热源,众多周知,它的存在可能会使流体内层之间出现共振从而导致不稳定.因此,通过推导方程组的先验界,得到了方程组的解对热源自身的收敛性.
Detached-Eddy Simulation of Flow Past Tandem Cylinders
ZHAO Wei-wen, WAN De-cheng
2016, 37(12): 1272-1281.   doi: 10.21656/1000-0887.370546
[Abstract](797) [PDF 3862KB](611)
摘要:
主要开发了SST-DES和SST-DDES两种分离涡方法,并集成到基于开源代码平台OpenFOAM开发的CFD求解器naoe-FOAM-SJTU中.选用高Reynolds(雷诺)数下串列双圆柱绕流问题作为标准算例来验证所开发的分离涡方法.该标准算例此前在美国国家航空航天局兰利研究中心的两个不同风洞做过物理试验.该研究将数值模拟得到的时均流场信息和一些其他物理量同物理试验结果比较,同时讨论分析了三维瞬态流场结构.结果表明该文开发的SST-DES和SST-DDES分离涡方法能够解决高Reynolds数下有大量流动分离的复杂流动问题.
Some New Advances in the Probability Density Evolution Method
LI Jie, CHEN Jian-bing
2017, 38(1): 32-43.   doi: 10.21656/1000-0887.370336
[Abstract](1143) [PDF 683KB](2049)
摘要:
介绍了随机动力系统中概率密度演化理论的基本方程与求解方法〖CX4〗.〖CX〗在此基础上,论述了广义概率密度演化方程求解的若干新进展,包括群演化方程及其求解、概率空间剖分的理性准则、点集加密技术与信息拓展方法等.
Simulation of Multi-Hydrofracture Horizontal Wells in Shale Based on the Extended Finite Element Method
CHEN Jun-bin, WEI Bo, XIE Qing, WANG Han-qing, LI Tao-tao, WANG Hao
2016, 37(1): 73-83.   doi: 10.3879/j.issn.1000-0887.2016.01.006
[Abstract](985) [PDF 1871KB](684)
摘要:
页岩储层水平井分段多簇压裂簇间距优选是压裂技术的关键,建立了水力压裂流固耦合数学模型,基于扩展有限单元法模拟多条裂缝的扩展过程,研究多条裂缝同时扩展的转向规律,以及应力干扰、水平主应力差、裂缝间距等因素与裂缝转向角度的关系.结果表明:应力干扰作用对裂缝宽度具有限制作用,单条裂缝张开宽度比两条裂缝的大;裂缝转角随应力差的减小而增大,随压裂时间的增加而增大.簇间距越小,应力干扰越强,转角越大,综合主缝均匀扩展、支撑剂填充以及复杂裂缝网络形成等条件,确定最优簇间距为30~40 m.多条裂缝同时扩展时,中间裂缝会受到两边裂缝的限制作用,簇间距越小,限制作用越强,裂缝发育时间越长,扩展速度越慢.
Analysis on Shear Deformation and Shear-lag Effects on Twin-Cell Box Girders
ZHANG Hui, ZHANG Yu-yuan, ZHANG Yuan-hai, LI Wei
2016, 37(8): 791-803.   doi: 10.21656/1000-0887.370056
[Abstract](812) [PDF 589KB](827)
摘要:
基于各个翼板选取不同的最大剪切转角差为剪力滞广义位移,应用能量变分原理分别推导出了考虑和不考虑剪切变形时单箱双室截面控制微分方程组,结合边界条件给出了箱梁纵向应力和竖向挠度的初参数解,从力学、数学角度上证实了剪切变形和剪力滞效应是两个相对独立的力学行为,进一步阐述了二者对箱梁的影响,即剪切变形对箱梁截面纵向应力无影响,但是对竖向挠度有很大的影响.数值算例表明,利用该文解和数值解分析跨中截面剪力滞系数横向分布规律,二者吻合程度良好,其横向分布规律与单室箱梁类似,唯独不同之处是边腹板处的剪力滞效应比中腹板处的剪力滞效应略微大一些;挠度计算表明,剪切效应使得该箱梁在集中和均布荷载作用下跨中挠度分别增大4.6%和2.7%.
Progresses in the Study on Vibration Damping Properties of Novel Lightweight Composite Sandwich Structures
MA Li, YANG Jin-shui
2017, 38(4): 369-398.   doi: 10.21656/1000-0887.370328
[Abstract](1225) [PDF 6800KB](1183)
摘要:
作为新一代先进轻质超强韧结构材料,复合材料格栅和点阵夹芯结构受到了国内外学者的广泛关注.目前关于该类结构材料的设计制备以及相关力学性能研究已取得了大量的研究成果.然而对该类结构振动阻尼性能的研究则处于起步阶段.该文综述了纤维增强树脂基复合材料简单层合结构以及各类夹芯结构振动阻尼性能的研究现状.首先阐述其阻尼机理, 然后分别概述了复合材料简单层合板的微观和宏观阻尼模型、复合材料粘弹性阻尼夹层结构和新型夹层结构的阻尼预报工作,最后总结归纳现有关于该类结构阻尼特性研究工作中已取得的成果和不足之处,并对其未来发展进行了展望.
Investigations of Self-Propulsion in Waves of Fully Appended ONR Tumblehome Model
WANG Jian-hua, WAN De-cheng
2016, 37(12): 1345-1358.   doi: 10.21656/1000-0887.370525
[Abstract](1130) [PDF 3993KB](551)
摘要:
采用基于重叠网格技术的CFD方法数值研究了全附体ONRT船模在迎浪工况中自航的水动力特性.文中数值计算采用自主开发的面向船舶与海洋工程的CFD求解器naoe-FOAM-SJTU.自航计算中船体运动及螺旋桨转动等通过重叠网格技术完成,波浪环境则采用求解器中的三维数值造波和消波模块实现.计算中自航船模的螺旋桨转速通过静水自航数值计算得出,波浪工况计算采用东京2015 CFD会议中标准算例进行设置.数值计算结果,如船体运动、实时航速变化等,与试验数据进行了对比分析.此外,给出了数值预报的推力和扭矩系数,并且通过详细的流场信息来分析和解释了船模在波浪中自航过程中的水动力变化情况.数值预报结果同试验值吻合较好,说明采用当前结合重叠网格技术和CFD的数值方法可以很好地预报波浪中自航问题.
Study of Stress Field Near Interface Crack Tip of Double Dissimilar Orthotropic Composite Materials
LI Jun-lin, ZHANG Shao-qin, YANG Wei-yang
2008, 29(8): 947-953.  
[Abstract](2993) [PDF 460KB](21)
Abstract:
A study of double dissintilar orthotropic composite materials interfacial crack was made by constivcting new stress functions and employing the method of composite material complex.In the case that the characteristic equations' discriminants are all more than zero,the theoretical fonmula of the stress field and the displacement field near the mode Ⅰ interface crack tip,without oscillation and inter-embedding between the interfaces of the crack were delved.
Second Order Approximation Solution of Nonlinear Large Deflection Problem of Yongjiang Railway Bridge in Ningbo
CHIEN Wei-zang
2002, 23(5): 441-451.  
[Abstract](5572) [PDF 395KB](119)
Abstract:
The solution and computational aspects on nonlinear deflection of Yongjiang Railway Bridge in Ningbo were investigated.An approximate iteration algorithm on nonlinear governing equation was presented,and the obtained results show that,if altitude difference and span of the riverbanks are taken as 5 meters and 100 meters,respectively,the maximum gradient in the middle of the bridge exceeds 5%,much larger than maximum allowance gradient in railway design code.Therefor,a new solution scheme for decreasing gradient of the bridge is put forward,that is,the altitude difference between two riverbanks can be decreased to about 1/10 of the initial magnitude by building roadbeds with 0.5% gradient and 1 kilometer length at two riverbanks.As a direct result,the deflection gradient of the railway bridge is much reduced and the value is between 0.5%~0.6%.